The Cisco uBR10012 router can be configured to require all CMs to return a known text string to register with the CMTS and gain access to the network. The text string can be from 1 to 80 characters in length. To activate CM authentication, use the following command from cable interface configuration mode.

To configure authentication and data privacy parameters, use the cable shared-secret command in cable interface configuration mode. To disable authentication during the CM registration phase, use the no form of this command.

cable shared-secret [0 | 7] authentication-key

no cable shared-secret

The following example shows how to activate CM authentication using 3344912349988...sf as the shared secret key and indicating that an encrypted message follows:

Router(config-if)# cable shared-secret 7 3344912349988cisco@xapowenaspasdpuy230jhm...sf

When a CM is ready to transmit data, it requests a channel from the Cisco uBR10012 router. You can limit the amount of time that a CM requests a channel for the first time from the Cisco uBR10012 router. A CM's initial channel request is known as insertion. The valid range is 100 to 2000 milliseconds.

To activate the CM insertion interval, use the following command in cable interface configuration mode.

cable insertion-interval milliseconds

The Cisco uBR10000 series CMTS can be configured to require all CMs to return a known text string to register with the CMTS and gain access to the network. The text string can be from 1 to 80 characters in length. The default setting is "on" (CM authentication is activated).

To activate CM authentication, use the following command in cable interface configuration mode:

cable shared-secret [0|7] authorization-key

 no cable shared-secret

Tip

Be sure that you enter the correct slot and port number in cable interface configuration mode. Verify that the CM is using baseline privacy interface (BPI) and that it is assigned to a quality of service (QoS) with privacy active. Verify that the cable interface configuration file contains a matching key.

CM upstream address verification ensures that only CMs that have received Dynamic Host Configuration Protocol (DHCP) leases through the Cisco uBR10012 router can access the HFC network. The Cisco uBR10012 router discards all packets received from or for hosts that have not received Dynamic Host Configuration Protocol (DHCP)-assigned addresses. The default setting is "off" (CM upstream address verification is deactivated).

To activate or deactivate CM upstream verification, use the following command in the cable interface configuration mode:

cable source-verify [dhcp]

no cable source-verify

To clear the counters for the CMs in the station maintenance list, use one of the following commands in cable interface configuration mode.

clear cable modem 
mac-addr 
counters
 

clear cable modem
 ip-addr 
counters

clear cable modem all counters

To remove one or more CMs from the station maintenance list and reset the cable modem (or all CMs) on the network, use one of the following commands in cable interface configuration mode.

clear cable modem mac-addr reset 

clear cable modem ip-addr  reset

clear cable modem all reset

By default, registered CMs that have no upstream activity for three minutes are timed out and disconnected from the Cisco uBR10012 router. This timeout interval can be decreased to 2 minutes or increased up to 60 minutes.

To specify the registration timeout interval for CMs connected to the Cisco uBR10012 router, use the following command in cable interface configuration mode.

cable registration-timeout
n

The Cisco uBR10000 series software includes the following algorithms that control the capacity of the contention subchannel and control the efficient use of a given contention subchannel capacity:

• Algorithm that dynamically controls the rate of upstream contention slots—initial ranging and bandwidth requests.
• Algorithm that varies the backoff parameters that CMs use. Backoff variation falls within each of the initial ranging and bandwidth request upstream contention subchannels.

In high contention mode, the Cisco uBR10000 series MAC scheduler uses collision statistics and sustains a high frequency of initial ranging slots until it detects a steady ranging state. The CMTS dynamically varies the frequency of initial ranging slots using the data grant utilization on the upstream channels. The CMTS trades upstream bandwidth between data grants and initial ranging slots. The CMTS autodetects a high collision state and switches to low insertion interval mode after a steady state is achieved where few collisions occur.

The CMTS is careful when monitoring the ranging channel health to revert to a steady state. In steady state mode, data grants—grant utilization—receive preference over initial ranging slots.

Although the binary exponential backoff algorithm operates in a distributed fashion at different CMs, the CMTS provides centralized control for the backoff algorithm. To achieve this, it remotely monitors traffic load—the backlog developing on the contention channel—and then varies the backoff start and end specified in the MAPs for that upstream channel. This ensures that colliding CMs are properly randomized in time.

The following cable interface commands are available to configure the dynamic contention algorithms:

[no] cable insertion-interval [automatic [Imin [Imax]]] | [msecs]
[no] cable upstream port num range-backoff [automatic] | [start end]
[no] cable upstream port num data-backoff [automatic] | [start end]

A Cisco CMTS administrator can enhance the upstream throughput from a CM connected to the Cisco uBR10000 series CMTS. The system employs a new algorithm that automatically tunes the lookahead time in MAPs, based on several input parameters for the corresponding upstream channel. The use of dynamic and optimal lookahead time in MAPs significantly improves the per-modem upstream throughput.

Caution

Only a trained Cisco CMTS administrator should adjust these values.

To configure the dynamic map advance algorithm, use the following command in cable interface configuration mode.

cable map-advance dynamic [n]|static

Caution

If you are adjusting the dynamic map-advance algorithm, do not reduce the safety factor below the default value of 1000 usecs in a production network, until you are confident that the reduced safety factor suffices for your deployment. The default value is chosen to be a safe operating point for the algorithm.

To specify the maximum number of hosts that can be attached to a subscriber’s CM, use the following command in cable interface configuration mode.

cable max-hosts n
no cable max-hosts

You can configure the Cisco uBR10012 router to filter incoming packets from individual hosts or cable interfaces based on the source Media Access Controller (MAC) or Internet Protocol (IP) address. Definition of filters follows standard Cisco IOS configuration practices for access lists and groups.

Note	Configuring per modem or host filters is supported in Cisco IOS Release 12.0(5)T1 or higher, as well as in Cisco IOS Release 12.0(6)SC or higher.

To configure per modem filters, use the following commands in cable interface configuration mode.

To specify the sync message interval between successive sync message transmissions from the Cisco uBR10012 router, use the following command in cable interface configuration mode.

cable sync-interval msec
no cable sync-interval